1. Field of the Invention:
The invention is related to the removal of volatile contaminants, such as organic contaminants, from underground soil or water.
2. Background Art:
Various conventional techniques are used to cleanse soil or underground water of contaminants caused by underground pollution. Such contaminants are generally hydrocarbon or organic pollutants, although various chemical pollutants are extracted with the conventional techniques. One technique is in situ water treatment, in which an injection well and an extraction well are dug over the site of a polluted underground water table. The injection well is dug to a depth at or below the height of the water table. Heated air or carrier gas is pumped into the injection well, while a vacuum is applied to the extraction well. The heat and carrier gas causes the contaminants in the underground water to volatize out of the water and travel through the soil from the injection well to the extraction well, where the vacuum sucks the contaminants out as vapor. A related technique is in situ soil treatment, in which the injection well does not penetrate down to a water table, and the contaminants are principally volatized out of the soil between the injection and extraction wells.
Another technique is ex situ soil treatment, in which underground contaminated soil is drawn into a kiln, where it is heated and stirred. The heat volatizes the contaminants out of the soil in the kiln. A vacuum pump draws the volatized contaminants out of the kiln as vapor. The heated soil must be cooled upon exiting the kiln. A related technique is ex situ water treatment, in which underground contaminated water is sparged by passing it through a sparging tank in which a carrier gas is bubbled through the contaminated water. Contaminatants in the water are captured in the air bubbles, which are drawn off as a vapor by a vacuum as they reach the surface of the water in the tank. This process may be enhanced by heating the water upon entry into the sparging tank. To avoid thermal pollution, heated water must be cooled upon exiting the sparging tank.
The contaminants in the vapor created by each of these treatment techniques is recovered by condensing the contaminants therein into liquid form and also by carbon filtration. The condensing requires a refigeration unit to cool the vapor. In carbon filtration, the carbon is regenerated by purging with a hot gas pumped through the carbon chamber, the gas exiting the carbon chamber containing contaminants. This gas itself may be purged by condensing the contaminants therein.
The disadvantage of the foregoing techniques is that they require large amounts of heat and power. The generation of such heat and power itself creates pollution, and furthermore consumes energy and is expensive. Thus, these conventional techniquese are inefficient, and their use is confined therefore to only those applications in which the amount of pollution justifies the penalties in energy consumption, cost and pollution. Thus, such techniques have been of limited use and application.
Accordingly, it is an object of the invention to provide in situ and/or ex situ soil and/or water treatment without the foregoing limitations in efficiency, particularly with regard to energy consumption and cost. It is a further object of the invention to reduce net amount of heat generated in a soil or water cleansing treatment.